The economic threat that's kept many Americans on edge for months is nearing reality - unless the White House and Republicans cut a budget deal by New Year's Day.

Congressional officials said Wednesday (US time) they knew of no significant strides toward a compromise over a long Christmas weekend, and no negotiations have been set.

President Barack Obama decided to cut short his Hawaii vacation for an overnight flight expected to get him back to the White House in the pre-dawn hours of Thursday (US time), when members of Congress return to Washington.

After weeks of negotiations, the president urged lawmakers late last week to scale back their ambitions and send him legislation preventing tax cuts on all but the highest-earning Americans and extending unemployment benefits for the long-term jobless. Longer, term, he said he still supports deficit cuts that were key to the earlier talks.

Huge tax increases. Deep cuts in domestic and defence programmes. The likelihood of sinking stock prices, reduced consumer spending and corporate layoffs. The risk of a recession within months.

Still, the start of 2013 may turn out to be far less bleak than feared. For one thing, the two sides may strike a short-term agreement before New Year's that postpones spending cuts until spring.

Even if New Year's passed with no deal, businesses and consumers would not likely panic as long as some agreement seemed imminent. The US$671 billion (NZ$820b) in tax increases and spending cuts could be retroactively repealed.

And the impact of the tax increases would be felt only gradually. Most people would receive slightly less money in each pay cheque.

"The simple conclusion that going off the cliff necessarily means a recession next year is wrong," says Lewis Alexander, an economist at Nomura Securities. "It will ultimately depend on how long the policies are in place."

It's always possible that negotiations between President Obama and Republican congressional leaders will collapse in acrimony. The prospect of permanent tax increases and spending cuts could cause many consumers and businesses to delay spending, hiring or expanding.

Without any agreement at all for months, the fiscal cliff would cause the US economy to shrink 0.5 per cent in the first half of 2013 and fall into recession, the Congressional Budget Office estimates.

But most economists expect a deal, if not by New Year's then soon after. Businesses and consumers will likely remain calm as long as negotiators seem to be moving toward an agreement.

"The atmosphere is more important than whether the talks spill" into next year, said Paul Ashworth, an economist at Capital Economics.

Here's why many are optimistic that a brief fall over the cliff wouldn't derail the economic recovery:

- Though the fiscal cliff would boost taxes by US$586b for all of 2013, the tax hit for most people would be modest at first. The expiration of Social Security (the federal pension programme) and income tax cuts would be spread throughout 2013. For taxpayers with incomes of US$40,000 to US$65,000, pay cheques would shrink an average of about US$1,500 next year. That would be a significant bite over the full year, but the initial hit would be just US$130 in January, according to the nonpartisan Tax Policy Center.

- About a third of the tax increases wouldn't touch most Americans. Some would hit businesses. Others, such as higher taxes on investment income and estates, and the expiration of middle-income tax credits, wouldn't come due until Americans filed their 2013 taxes in 2014.

- The Internal Revenue Service has delayed any increases in tax withholding that would otherwise kick in. Without a deal, the top income tax rate for single people with taxable income between about US$36,000 and US$88,000 would rise from 25 per cent to 28 per cent. But that won't start to reduce Americans' pay cheques in early January, even if no deal is reached by then.

- About US$85b in spending cuts to defence and domestic programmes would take weeks or longer to take effect. That means government agencies wouldn't cut jobs right away.

If a short-term agreement is struck, some taxes would probably still go up. These would include a 2 percentage point cut in Social Security taxes that's been in place for two years. Its expiration would cost the typical household about US$1,000 a year. With income gains sluggish, that could dampen consumer spending.

A temporary deal that delays some hard decisions could reduce business and consumer confidence. It would also mean:

- Extended unemployment benefits would end for 2 million people. The federal government's program pays for about 32 weeks of extra benefits, on average, on top of the 26 weeks most states provide. Weekly unemployment checks average about US$320 nationwide.

- The stock market would probably drop, though maybe not by much. Many Wall Street analysts expect a partial deal of some kind. "There is starting to become a little bit of an acceptance that we fall off the fiscal cliff," said J.J. Kinahan, a strategist for TD Ameritrade.

- The expiration of the Social Security tax cut and the end of emergency unemployment benefits would likely shave 0.7 of a percentage point off economic growth next year, the CBO estimates. The economy is now growing at about a 2 per cent annual pace.

If no deal at all was reached by January and budget talks dragged on, many businesses might put off investment or hiring. That's why most economists say it would be crucial to reach a deal within roughly the first two months of 2013.

The gravest scenario would be if the budget talks collapsed and the tax increases and spending cuts appeared to be permanent.

In that case, Macroeconomic Advisors warns that the Dow could plunge up to 2,000 points within days. Businesses would turn gloomier in anticipation of Americans paying higher taxes and spending less.

The economy would shrink at an annual rate of 0.6 per cent in the first three months of 2013, estimates Joel Prakken, an economist at Macroeconomic Advisors. That compares with an estimated 1.9 per cent growth rate if a deal is reached. CBO forecasts that the unemployment rate would rise to 9.1 percent from the current 7.7 per cent.

Last week, Obama and House Speaker John Boehner narrowed their differences on income tax increases and spending cuts. But with the two sides deadlocked, Boehner scheduled a vote on a bill to prevent taxes from rising on those earning less than US$1 million a year. Opposition from anti-tax conservatives, and Democrats, forced him to cancel the vote.

Obama called for a vote on a stripped-down agreement that would raise taxes only on the wealthiest 2 per cent of Americans and extend emergency unemployment benefits. Automatic spending cuts would be postponed.

Whatever the outcome, some trends could offset part of the economic damage. The average retail price for gasoline has dropped 15 per cent this fall, for example. Lower gas prices give consumers more money to spend elsewhere.

And if the crisis is resolved, as many expect, the boost to business and consumer confidence would encourage more hiring and spending.

"We could end up with a much more robust recovery than anybody's envisioned" if a deal is reached, said David Cote, CEO of Honeywell International.